Abstract:
The analysis of data and design of flexible pavement in Bangladesh by conventional
flexible design procedures is mostly based on the basis of test and field condition
prevailing in western countries. These procedures do not comply with the environmental
and material conditions of the region. These conditions generally do not match the
parameters for design used in Bangladesh and south Asia. The result is often overdesigned
being uneconomical or under-design resulting in heavy maintenance and
rehabilitation costs. In this study climatic condition of the region is considered during the
design. Coarse grained river sand shall be used as subgrade material. In this design mostly
accepted conventional methods for flexible pavement design are compared to check their
adaptability for design input condition prevailing in countries of Southeast Asia. For
evaluation of flexible pavement design methods for Bangladesh, two currently used
methods are selected, i.e., AASHTO 1993 Guide for Design of Pavements structures
developed in the U.S.A. and Overseas Road Note 31 from Britain. Indian Road Congress
(IRC 37) is also considered for this study for comparison. Pavement structures are
designed by all the methods using same input parameters obtained from Bangladesh. The
results indicate that both methods recommend nearly equal total thickness. However,
AASHTO 1993 procedure suggests thicker concrete layer. whereas Road Note 31 and
IRC 37 suggest thicker base and sub-base layers. Mechanistic responses in terms of
stresses, strains and deflections at critical points in the pavement structure are calculated
by computer program CIRCLY. The damaging factors are calculated using CIRCLY
software. Mechanistic responses are usually related to failure modes in pavement. These
failure modes generally are rutting, permanent deformation, fatigue and thermal cracking.
The results of both methods show that structures designed by AASHTO 1993 procedure
are safer against rutting, permanent deformation. fatigue and thermal crack failures. The
thicker base and subbase layers suggested by Road Note 31 and IRC 37 to compensate for
thinner asphalt concrete layer do not significantly contribute to lowering of stresses. The
structures recommended by Road Note 31 and IRC 37 may cost less in the beginning due
to lesser asphalt concrete layer thickness, but may fail permanently requiring higher
maintenance and rehabilitation costs.
Description:
This thesis is submitted to the Department of Civil Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering, December 2015.
Cataloged from PDF Version of Thesis.
Includes bibliographical references (pages 77-79).